In analytical laboratories, it is common practice to "seal" bottles of HPLC solvents simply with a perforated aluminium foil or plastic cap. Connecting tubes are inserted into the bottles through the holes in the foil/cap without any additional sealing. To test for the reproducibility of the retention time and the loss of solvent by evaporation, tests were performed over a period of 31 days. The separation of three PAHs (Polycyclic Aromatic Hydrocarbons) with solvents, stored in either tightly closed bottles (SafetyFirst Caps) or bottles closed with caps with holes of different diameters, was compared. The results of the tests were dramatic. Summarized: The new SafetyFirst Caps significantly improve health protection and reproducibility of test readings.